Among the most important and least understood properties of human brain function is that of top-down control of perceptual and cognitive operations. Cognitive control is what makes people intentional beings rather than stimulus-response automata. The aim of the proposed research is to investigate the neural basis of attentional control in the human visual system using functional magnetic resonance imaging (fMRI) and suitably designed cognitive paradigms. We have chosen to focus on the visual system because it is arguably the most well understood neural system (at least from a bottom-up perspective), and this knowledge base can be used to guide experiments that investigate top-down control. Much recent work in cognitive neuroscience has revealed the extent to which the neural response of early perceptual regions of the brain (e.g., V1, V4, MT, the Fusiform Face Area) can be modulated by top-down attentional control. However, while these studies of the effects of attentional control are crucial pieces to the puzzle, very few studies have focused on the source of attentional control signals. This is the primary focus of the proposed project. The specific aims of the project include (1) investigating the neural circuits that are involved in focused attention and in controlling shifts of attention between spatial locations; (2) investigating the control of object-based and feature-based selection, and determining whether they share an anatomical locus with that for location-based selection; and (3) investigating the frontal and posterior areas that control both task-shifting and attention-shifting. Together, the proposed project will significantly advance our understanding of how attentional control is exerted to modulate sensory input, and this in turn will contribute to theories of cognitive control throughout the brain.